This application claims the benefit of Korean Application No. 2002-1974, filed Jan. 14, 2002, and Application No. 2002-60510, filed Oct. 4, 2002, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a refrigerator and a method of controlling the same, and more particularly, to a refrigerator which performs a defrosting operation using a microcomputer having a common input port and a plurality of bimetals, and a method of controlling the same.
2. Description of the Related Art
Generally, refrigerators prevent the decomposition of foods stored therein and maintain the freshness of the foods for a lengthy period of time by compulsorily supplying cool air generated from an evaporator to a refrigerator compartment using a fan.
In such a refrigerator, an evaporator and a fan which generate cool air and supply the cool air to a freezer compartment and a refrigerator compartment are installed in a back portion of a body. That is, the evaporator and the fan perform a cooling operation by supplying the cool air to the freezer compartment and the refrigerator compartment. Alternatively, a refrigerator may have an evaporator and a fan for each of a freezer compartment and a refrigerator compartment. The evaporators and the fans perform a cooling operation by independently supplying cool air to the corresponding freezer compartment and the refrigerator compartment. In either of the above refrigerators, a defrosting operation to eliminate frost, which is stuck to an evaporator, is performed by driving a defrost heater arranged on the evaporator.
The defrosting operation is carried out under a control of a microcomputer which entirely controls a refrigerator. The defrosting operation is performed such that defrosting conditions to determine whether the defrosting operation is performed are previously set, and the defrost heater is driven in response to the corresponding defrosting conditions being satisfied.
The conventional refrigerator, as described above, is constructed such that after the defrost heater is driven to start a defrosting operation, the microcomputer receives a defrost temperature (a surface temperature of an evaporator) sensed through a temperature sensor mounted on the evaporator, and stops the driving of the defrost heater where the sensed defrost temperature reaches a set temperature.
FIG. 1A shows a conventional refrigerator, and FIG. 1B shows a flowchart to illustrate a method of controlling the refrigerator of FIG. 1A.
As shown in FIG. 1A, the refrigerator includes a thermistor TH which is mounted on an evaporator (not shown) and has a resistance that varies according to a defrost temperature, a voltage dividing resistor Ra which is connected to the thermistor TH, and a resistor Rb and a capacitor Ca which are connected to an input port P1 of a microcomputer 1. The resistor Rb and the capacitor Ca drop a voltage divided by the resistor Ra and stabilize the voltage.
With reference to FIG. 1B, a defrosting operation of the refrigerator shown in FIG. 1A will be described below.
Where defrosting operating conditions are satisfied, the microcomputer 1 turns on a defrost heater (not shown) so as to start a defrosting operation, in operation 10. A defrost temperature increases due to a heat generated by the defrost heater, and accordingly, the heat melts frost stuck to the evaporator. In this case, a voltage corresponding to a resistance value of the thermistor TH, which is varied according to the defrost temperature, is input to the input port P1 of the microcomputer 1 in operation 20. The microcomputer 1 converts the input voltage detected through the input port P1 into digital temperature data, and calculates a defrost temperature on the basis of the digital temperature data in operation 30.
The microcomputer 1 determines whether the calculated defrost temperature corresponds to a set temperature, that is, a defrosting stop temperature, to stop the defrosting operation, in operation 40. Where the calculated defrost temperature does not correspond to the defrosting stop temperature in the operation 40, the microcomputer 1 continues to perform the defrosting operation. Where the calculated defrost temperature corresponds to the defrosting stop temperature, the microcomputer 1 turns off the defrost heater so as to stop the defrosting operation, in operation 50, and returns to an operation of cooling respective compartments of the refrigerator.
However, the conventional refrigerator is problematic in that it senses a defrost temperature using a single thermistor TH mounted on the evaporator. Accordingly, inexact defrost temperature may be sensed, causing a defrosting operation to be stopped prematurely, and leaving some of the frost still stuck to a portion of the evaporator.
In view of the above, FIG. 2 shows and Korean Patent No. 161925 (Korean Laid-Open Publication No. 1997-22128) discloses a method of checking a defrost temperature that is close to an actual temperature of an evaporator 2 by mounting defrost temperature sensors 6a and 6b on both side portions of the evaporator 2. The temperature sensors 6a and 6b are used to more accurately sense a surface temperature of the evaporator 2.
However, the conventional refrigerator of FIG. 2, as described above, has a complicated construction and is costly to manufacture. That is, in addition to expensive temperature sensors, a microcomputer of the refrigerator necessarily has additional input ports that are connected to the respective temperature sensors. In other words, as the number of added temperature sensors is increased, the number of the input ports of the microcomputer is increased proportionally in the conventional refrigerator. Accordingly, the refrigerator having the above structure also has a complicated circuit construction that performs a defrost temperature sensing operation.
Accordingly, it is an aspect of the present invention to provide a refrigerator having a simplified circuit construction which checks a defrost temperature using one or more temperature sensing devices, and a method of controlling the same.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other aspects of the present invention, there is provided a refrigerator which performs a cooling operation and a defrosting operation, comprising an evaporator to perform the cooling operation, a defrost temperature sensing unit which includes a plurality of temperature sensing devices, wherein the temperature sensing devices are mounted on the evaporator to be spaced apart from each other and the defrost temperature sensing unit senses a defrost temperature using the temperature sensing devices, and a microcomputer having a common input port which receives the defrost temperature detected by the defrost temperature sensing unit.
To achieve the above and other aspects of the present invention, there is provided a method of controlling a refrigerator which senses a defrost temperature using a plurality of temperature sensing devices, which are mounted on an evaporator to be spaced apart from each other, and performs a defrosting operation to defrost the evaporator according to a control of a microcomputer having a common input port to receive the sensed defrost temperature, the method comprising determining operating states of the temperature sensing devices on the basis of the defrost temperature input through the common input port in the defrosting operation, and stopping the defrosting operation in response to the defrost temperature corresponding to defrosting stop conditions on the basis of determined results for the operating states of the temperature sensing devices.
In the present invention, one or more temperature sensing devices are mounted on the evaporator so as to sense a defrost temperature (a surface temperature of the evaporator). The temperature sensing devices may be implemented by bimetals having the same operating characteristics, or by two kinds of devices, for example, a thermistor and a bimetal, having different operating characteristics. The operating characteristics of the bimetals include being turned on or off according to the defrost temperature. The operating characteristics of the termistor include having a resistance thereof which is varied according to the defrost temperature.